Slow speaker cables?

12-11-12: B_limo
Al, how do you know so much about all of this!?! I see you posting responses to questions all the time here; you seem like a genius to me.

Thanks, B. I have an extensive background in electronic design, both analog and digital, although in defense electronics, not audio. And I've been an audiophile since around 1980. And I enjoy getting into the technical aspects of the hobby.

Best regards,
-- Al

Differences in inductance can, at least to a slight degree, affect frequency response in the upper treble region, especially if the impedance of the speaker is low at those frequencies. Greater high frequency extension = "faster."

Differences in resistance can affect woofer damping and bass response. Better woofer damping and better controlled bass response = "faster."

Differences in capacitance, if extreme enough, can affect amplifier performance, especially at high frequencies that relate to perceived "speed."

Differences in antenna effects, and "transmission line" effects that occur at inaudible RF frequencies, can result in differences in spurious energy that may enter the feedback loop of the amplifier, if it has one, with unpredictable consequences.

There are undoubtedly other reasons as well, although not necessarily the reasons that are stated in the "white papers" of some cable manufacturers. And none of these reasons necessarily mean that "more expensive" = "better."

Regards,
-- Al

12-11-12: Csontos
Some of the best sounding amps have limited bandwidth. I don't understand how greater high frequency extension="faster". Is it not rise time that ultimately determines the perceived speed of the amp at the upper end of the scale? Not taking you to task Al.

That is a legitimate question, Peter.

First, bandwidth and risetime are intimately related. Oversimplifying somewhat, the greater the bandwidth the faster the risetime.

But what I was referring to was primarily greater high frequency extension within the 20 kHz audible spectrum. Under some circumstances speaker cable inductance can produce an audibly perceptible rolloff of frequencies that are within that range. Particularly, as I said, if the impedance of the speaker is low at those frequencies. Electrostatics, for instance, commonly descend to the area of 1 ohm at 20 kHz, as I'm sure you realize. The inductive reactance of a speaker cable (inductive reactance being the inductive form of impedance, which is measured in ohms and is proportional to frequency), can be a significant fraction of that value at upper treble frequencies, particularly if the cable length is long and/or the cable does not have low inductance per unit length. The voltage divider effect resulting from the interaction of those two impedances will, to at least a small degree, roll off the upper treble.

Rolloff of the upper treble will, of course, tend to be perceived as sluggish transient response, and probably dullness as well.

Bandwidth limitations beyond 20 kHz, either in the amplifier or resulting from the interaction of cable inductance and speaker impedance, may also have audible effects, due to phase shifts of audible frequencies that will increasingly occur as bandwidth is reduced. That is one reason, btw, that amplifier bandwidth needs to extend considerably beyond 20 kHz.

Another factor necessitating bandwidth margin in the amplifier is, I believe, minimization of feedback-induced TIM (transient intermodulation distortion), if the amplifier uses feedback. Transient response that is sloppy and distorted as a result of TIM might also contribute to a perception of sluggishness, but that gets into amplifier-related matters that are not germane to this discussion.

Best regards,
-- Al

Michael, David, thank you kindly.

Csontos, probably the only times I've had friendly disagreements with the opinions of my learned A'gon colleague Kijanki is with respect to cable-related matters such as skin effect and "strand jumping," both of which I tend to be skeptical about, although I remain at least a little bit open-minded about those issues.

Both questions could be the subject of extensive debates, with the end result probably being that a conclusively proven conclusion cannot be reached, notwithstanding the many claims and "white papers" that have been issued by cable manufacturers.

Also, if I understand correctly, you are saying that the 8 awg 500 strand wire resulted in improvements in both power wiring and speaker cable applications. As you no doubt realize, the technical considerations, and the wire parameters that are most likely to be optimal, are very different for the two applications. An increase in inductance in power wiring, for example, involves a tradeoff between the benefits it may provide in filtering out high frequency noise, vs. the downside it may have of reduced responsiveness to abrupt changes in demand for current. The bottom line on those tradeoffs probably figures to be amplifier dependent, in part because the degree of fluctuation in current demand will vary dramatically among Class A, Class AB, and Class D amplifiers.

In any event, I don't doubt that the improvements you realized with the specific cables you described were real. I would just question the reasons for those improvements, and, to the extent that those reasons are in doubt, the applicability of your findings to other situations.

Best regards,
-- Al

12-12-12: Csontos
Al, does the fact that I'm hearing an improvement rather than just verifying one on instrumentation outweigh any negative impact on the amp? Doesn't the fact that we're dealing with wire no more than 6" long render inductance a non-issue? I'm guessing the Acoustat amps were built this way for the reason you mentioned. But also with the ability to drive low impedance loads such as the Acoustat speakers. So does it not stand to reason inductance is not an issue?

Not sure what you mean by "negative impact on the amp," but I would not doubt that you may have heard an improvement that would not have been verifiable even with sophisticated instrumentation.

Yes, I would expect the 6 inch length to most likely make inductance a non-issue. When I submitted my earlier comment I missed that fact that you were referring to internal wiring of such short length. A short length of heavy gauge wire like that would also nullify or greatly minimize pretty much all other cable effects that I can envision as being of possible relevance, including not only resistance, inductance, and capacitance, but also skin effect, strand jumping, dielectric absorption, RF "transmission line" effects, etc., to the extent that they might have had any relevance at longer lengths.

My research seems to corroborate my experience that replacing power supply wiring with 8awg, 500 strand is a significant overall improvement.

Assuming that the previous wiring was not poorly chosen in some way, such as being marginal in gauge, and that it had not suffered some sort of age-related degradation, and assuming that the previous solder joints were good, the only explanation that occurs to me for the improvement you perceived is that minor differences in physical placement of the old wiring vs. the new wiring might have affected coupling of noise transients (perhaps associated with current surges caused by abrupt changes in the power demands of the music) to or from other circuit points. Perhaps there are other reasons, but it's hard to say without having knowledge of the specifics of the design.

Excellent comments by several of the others above.

Best regards,
-- Al